Loss of junctophilin-3 contributes to huntington disease-like 2 pathogenesis
Version of Record online: 24 FEB 2012
Copyright © 2012 American Neurological Association
Annals of Neurology
Volume 71, Issue 2, pages 245–257, February 2012
How to Cite
Seixas, A. I., Holmes, S. E., Takeshima, H., Pavlovich, A., Sachs, N., Pruitt, J. L., Silveira, I., Ross, C. A., Margolis, R. L. and Rudnicki, D. D. (2012), Loss of junctophilin-3 contributes to huntington disease-like 2 pathogenesis. Ann Neurol., 71: 245–257. doi: 10.1002/ana.22598
- Issue online: 24 FEB 2012
- Version of Record online: 24 FEB 2012
- Accepted manuscript online: 17 AUG 2011 01:40PM EST
- Manuscript Accepted: 5 AUG 2011
- Manuscript Revised: 22 JUL 2011
- Manuscript Received: 4 JUL 2010
Huntington disease-like 2 (HDL2) is a progressive, late onset autosomal dominant neurodegenerative disorder, with remarkable similarities to Huntington disease (HD). HDL2 is caused by a CTG/CAG repeat expansion. In the CTG orientation, the repeat is located within the alternatively spliced exon 2A of junctophilin-3 (JPH3), potentially encoding polyleucine and polyalanine, whereas on the strand antisense to JPH3, the repeat is in frame to encode polyglutamine. The JPH3 protein product serves to stabilize junctional membrane complexes and regulate neuronal calcium flux. We have previously demonstrated the potential pathogenic properties of JPH3 transcripts containing expanded CUG repeats. The aim of this study was to test the possibility that loss of JPH3 expression or expanded amino acid tracts also contribute to HDL2 pathogenesis.
Transcripts from the HDL2 locus, and their protein products, were examined in HDL2, HD, and control frontal cortex. The effect of loss of Jph3 was examined in mice with partial or complete loss of Jph3.
Bidirectional transcription occurs at the HDL2 locus, although expression of antisense transcripts with expanded CAG repeats is limited. Protein products with expanded amino acid tracts were not detected in HDL2 brain. However, JPH3 transcripts and full-length JPH3 protein are decreased in HDL2 brain, and Jph3 hemizygous and null mice exhibit abnormal motor function.
Our results suggest that the pathogenic mechanism of HDL2 is multifactorial, involving both a toxic gain of function of JPH3 RNA and a toxic loss of JPH3 expression. Ann Neurol 2012;71:245–257